This study examines the effect of moonlight intensity on deermouse (Peromyscus maniculatus) vulnerability to predation by short-eared owls (Asio flammeus).

Three nocturnal light intensities, labeled new moon, quarter moon, and full moon, were simulated in a flight chamber. Deermouse activity was observed and measured by an index of tracking intensity in the chamber's sand floor. The mice were then exposed to predation by a short-eared owl in each light intensity and search time, chase time, capture time, and the number of escapes/chase were measured.

The results reveal the adaptive significance of deermouse activity suppression in full moon light as an anti-predator response. The deermice reduced activity significantly in bright moonlight during the activity phases. During the predation phases, the owls' hunting effectiveness increased as moonlight waxed. The owls required significantly less time to search for and capture the mice as illumination increased.

The costs and benefits to both species are discussed relative to the prey's variation of activity with moonlight intensity.

Thermoregulatory responses to changes in photoperiod were studied in the âblindâ mole rat Spalax ehrenbergi (Nehring). Acclimation of cold-sensitive individuals to short photoperiod (8L:16D) at an ambient temperature (Ta) of 22 degrees C increased their thermoregulatory capacity in cold conditions, when compared to individuals which were acclimated to a photoperiod of 12L:12D at the same Ta. Acclimation of cold-resistant individuals to Ta = 17 degrees C but with a photoperiod of 16L:8D caused a decrease in thermoregulatory capacity. Evaluation of the visual pathway through the visual-evoked potentials showed that the mole rat does not respond to flash stimuli and can thus be considered to be effectively blind.